Position indicator



' Aug. 25, 1925. T

E. M. HEWLETT ET AL POSITION INDICATOR Filed Sept. 15, 1921 Im/en-tors. Edward M- HewIe-Hr,

Waldo w Willard,

The ir- J -h-torne'g Patented Aug. 25, 1925.

UNITED STATES. PATENT nnwann M. HEWLETT AND w'ALno w. WILLARD, or SCHENECTADY," NEW Ydnx,

'AssIcNons TO GENERAL nnnc'rarcconmnx, acoarona'rron or NEW Yonx'i I rosx'rrolv mmcaron. I i 1 Application filed September 15, 1921. Serial No. 501,005.

To all wiwmt't may concern:

Be it known 'that we, EDWARD M. HEW- LETT and VV'AL Do- W. WILLARD, citizens of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful I Im rovements in; Position Indicators, of

Q of the sighting devices, the chart and the whichthe following is a specification.

This invention relates to position indicators and has for its object the'provision of a method of and means whereby the position in space of an object visible from two remote points can be determined.

More specifically, this. invention relates to 18 a system of automatictriangulation whereby observations of an aerial object, such as an aeroplane, can betaken from two known points on the ground and the lines of sight reproduced in a. convenient receiving station .to scale with relation to a chart so .as to indicate the position of the object both in altitude and azimuth.

In carrying out our invention, we employ two sighting devices located on a base line at a known distance from each other. At a receiving station located at some convenient place are two receiving devices each provided with a source of light and a reecting prism for throwinga beam of light on a chart of the field of observation.- The receiving devices are positioned on a base line which may be parallel to the base line receiving station base line being to scale.

Angular movements of the sighting'devices in both azimuth and altitude are transmitted to the respective receiving devices by means vof self-synchronoussystems, now known as selsyn systems, so that the beams ofligh t re-.

fiected yJthe receiving devices are automatically'directed parallel with the lines of sight of the sighting devices, respectively. The chart is held'in a horizontal plane over the receiving station base line and is adjustable to bring the point of intersection of thebeams of light on the chart. This spot of light indicates on the chart the po- I iticnlarly applica le to the. control of gun sition in azimuth of the object sighted upon,

and the distance between the chart and the receiving station base line represents the telescope.

height of the object. v

-In oneof its as ects, our invention is par fire upon an invisible target. In such a case the sighting devices may be located in conwheel 13. Spur gear 1 t meshes with a pinvenient positions of observation, such as in a trench, while the receiving devices'arelocated convenient to the gun. The gun :may be some distance in-the rear in a concealed position from which the Itargetcannot-be observed. From'the information in regard to the hei ht"and direction of the target transmltted from the points of observation and reproduced by the receiving devices, the gun can be properly directed on the, target. For a more complete understandin of our invention. reference should be hail to' the accompanying drawing in which Fig. 1 1s a dla'grammatic view of a position indicator embodying our invention. Fig. 2 is a slmphfied perspective view of the sightmg device; while Fig. 3 is a simplified perspective view of the receiving device.

Referring to Fig. 1 of the drawing, the V sighting devices A and A are located a convenlent dls'tance apart, such as a mile, on a known base line 10. In a convenientmay be remote from the sighting devices, are located two receiving instruments B and B having a base line '11 parallel with baseline 10 and of I a length to scale therewithfsuch as 5.28 feet.

omen.

receiving station, such as a dugout, which A chart C of the field of observation covered by the sighting devices is held by 'vertical supporting rod or bracket 10" in Referring to-Fig2, the sighting device 9 A consists of a to es cope 12 whichis su ported on a spindle 13 so as to be movab 6 about a horizontal axis perpendicular to the line of sight of the telescope, this axis being the axis of a spur gear 14 adjustably attached thereto. The telescope may be adjusted about its'horizontal axis with re-.

lation to gear 14 by adjusting screws 12? carried in lugs 14' onthe gear and engaging opposite sides of an arm'1'5 secured to the The telescope is rotatable with the spindle 13 about the axle of the spindle, which is maintained vertical, by means of .a. band ion on the shaft of a selsyn generator 16.

A spur gear 17 is adjustably secured to spindle 13 by means of a screw 17* which extends through an arc-shaped slot in a flange 155 on thespindl'e. Meshing with the gear 17 is a pinion 18 on the shaft of a selsyn generator 19. Selsyn generators 16 and 19 may be identical in construction, having single phase rotor windings 20 and 21 and three phase stator windings 22 and 23 (see Fig.1).

Referring to Fig. 3 of the drawing, the receiving instrument B consists of a reflecting prism 36 which is mounted on a spindle 24 so as to be movable about the axis, which is maintained horizontal, of a shaft 25 to which the'prism is secured. A collimated beam of light is projected on the prism through lens 37 from a source of light 38. The lens 37 and source of light 38 are held in fixed relation to the prism. As shown, the source of light 38 consists of an incandescent lamp which is mounted in a box 38 secured to a base or platform 38 carried by the spindle 24. The lens 37 is mounted in a suitable aperture in the box through which the light is directed on the prism. To provide ventilation for the lamp :1. false bottom 38 and top 38 are provided for the box secured in spaced relation therewith by means of suitable bolts. rangement also provides for access to the interior of the box in case it is desired to renew thelamp. The prism is also rotatable with the spindle 24 about the axis of the spindle, which is maintained vertical. The

. point of reflection of the prism is coincident with the intersection of the horizontal and vertical axis of the prism. Secured to shaft 25 is a spur gear 26 which meshes with a pinion 27' on the shaft of a selsyn driving motor 28. The spindle 24: is rotated about its vertical axis by means of a gear 29 secured thereto and meshing with a pinion. 30 on the shaft of a selsyn driving motor 31. selsyn motors 28 and 31 may be identical in construction with selsyn generators 16 and 19, having single phase rotorwindings 32 and 33 and three phasest-ator' wind-" ings 3 1 and 35 (see Fig. 1).

Like points of the stator windings 22 and 34 are interconnected by conductors a, b, and a, while like pointsof stator windings 23" and 35 are interconnected by conductors d, e, and f. The rotor windings 20, 21, 32, and 33 are energized from a suitable source of alternating current. The operation of systems of this general character in the transmission of angular movementis well known in the art. When the rotors of an interconnected generator and motor are in the same angular relation with respect to their stators, the voltages induced in the respective interconnected stator windings'by the cooperating field windings are equal and This ar- J The ratio betweengears 14 and15 is equal to the ratio between gears 26 and 27, and likewise the ratio between gears 17 and'18 is equal to the ratio between gears 29 and 30, so thatthe angular movement imparted to the receiving device by the selsyn motors is equal to the angular movement of the telescope.

The sighting device A and receiving device B are identical in construction with sighting device A and receiving device B,

and hence will not be described in detail. Like parts of these devices are indicated by prime reference numerals for the purpose of a clearer understanding.

The telescopes A and A are initially adjusted in altitude with relation to gears 14 and 14 by means of screws 12* and 12 and in azimuth with relation to gears 17 and 17 by loosening screws 17 and 17 and turning spindles 13 and 13 so that the lines of sight of the telescope are parallel respectively with the beams of light reflected by the receiving devices. The horizontal and vertical axes of the respective telescopes intersect atpoints which are the limits of base line '10. The limits of base line 11 are the points of reflection of the prisms.

Assumingthat it is desired to determine the position of an object in the air, suchas an aeroplane 39 which is within the field of observation of both sighting devices, the operation of our inventlon is as follows: The telescopes onthe sighting devices are directed at the aeroplane by rotating them about their horizontal and vertical axes. It

will be observed that the lines" of sight a andia of the sighting devices intersect at the'aeroplane. The beams of light I) and bare automatically moved by the selsyn motors to maintain their parallel relation with the linesof sight (1V and a, respectively. The intersection of the beams of light, therefore, represents the position in space of the aeroplane, with reference to base line 11; and this position is determined by moving chart C upward or downward until the point 'of intersection of the beams of light falls thereon at some point which indicates the position in azimuth of the aeroplane. To facilitate the vertical adjustment of the chart the support 10 may be threaded and slidably secured in a supporting base 40,

but splined or otherwise secured against rotatlon with respect to the base so that the projection of the miniature base line 11 onlowered to adjust the chart by means of a handwheel 42 turnin a gear43 cooperating with gear 41. To nd the height of the aeroplane, it is only necessary to find the distance to-scale from the chart tothe base line 11, since the triangle formed by beams of light 6, b, and base line 11 is similar to the triangle formed by lines of sight (1, a, and base line 10. It will be observed that this-distance is the distance from the chart .to the points of reflection of the beams of light.

The base line 11 has been taken parallel to base line 10 for the purpose of illustration, although the base lines need not necessarily be parallel. The projection of base line 11 on the chart, however, must be coincident with the representation of base line 10 on the chart. 1

Obviously, the selsyn motors may be used I to drive indicators, and the prisms adjusted by manual or other means to the positions indicated. Various methods may be used to determine the position of theintersection of the beams of llght.

.It will be observed that the length of base line 10 varies slightly with the position of the telescopes due .to the fact that the axes of collimation of. the telescopes do not exactly intersect the vertical axes' of the supports. This variation of the length of base line 10 is not so great as to cause an appreciable error, however.

Although we have shown and 'described selsyn systems .for the transmission of the angular movements of the sighting devices to the receiving devices, obviously any suitable synchronous system for the transmission of angular movement can be used.

In accordance vwith the provisions of the patent statutes, we have described the principle of operation .of our invention, together with the apparatus which we now consider to represent the best embodiment thereof,

but we desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means.

What we claim as new and desire to secure by Letters Patent'of the United States, is 1. The method of finding the position of an aerial object in terms of latitude, longi- .tude and height which consists in automatiobservation lines of sight to the object from two remote observation points, whereby the point of intersection of the beams represents the position in space of the object withreft so that said-beams reproerence to the chartfadjusting the chart in a direction corresponding to the vertical while maintaining its original orientation until the point of intersection of the beams falls thereon and indicates the position of the object in latitude and longitude, and then finding the perpendicular distance to scale from the chart to the point of origin of one of said beams to determine the height of the object.

2. A position indicator for aerial object's comprising a plurality of sighting devices, a plurality v of beams of light controlled thereby in directions to represent the lines of sight of said sighting devices so that when said sightingdevices .are directed. at an aerial object said beams of light are caused to intersect at a point representing the position in space .of the object, and a chart of the field of; observation of said sighting devices adjustable in a direction corresponding to the vertical to cause said point of intersection to fall thereon and indicate the position of the object in latitude andlongitude, the distance from the chart to the origin of one of said beams oflight representing the height of said object.v

3. A position indicator for aerial objectscomprising a plurality of'sighting devices, a plurality of controlled devices remote.

therefrom for projecting beams of light, systems .for the transmission of angular movements associated with said sighting devices and said controlled, devices, whereby the beams of light are caused to represent the lines of sight ofsaid sighting devices soitha't when said si hting devices are directed at an aerial ObIjGCt, said beams of light are caused to intersect at a point representing the position in space of the object, and a chart of the field of observation adjustable 'our hands this 14th day of September, 1921.

EDWARD M. HEWLETT. WALDO W. WILLARD." 

